Updated at 11:30 a.m.
Indiana Treasurer Richard Mourdock holds a single-digit lead over Sen. Richard Lugar, according to a poll conducted for the conservative group Citizens United, which is backing Mourdock in the primary.
Mourdock leads Lugar 44 percent to 39 percent in the poll, released with just under two weeks to go until the primary.
About 38 percent of Republican voters surveyed said they held a favorable opinion of Mourdock while 28 percent said they held an unfavorable opinion. Thirty-four percent had no opinion of him. Forty-four percent said they held a favorable opinion of Lugar of while 43 percent said they held an unfavorable view of him. Twelve percent said they had no opinion about the senator.
The last live-caller survey on the GOP race released publicly was a Mourdock internal poll conducted April 16-17 that showed a virtual tie between Lugar and Mourdock.
Outside groups continue to spend heavily on the primary. This week alone, the pro-Mourdock Club For Growth bought over $400,000 worth of air time for a new negative ad against Lugar while the pro-Lugar American Action Network released a new TV ad hitting Mourdock.
"All along, the Mourdock campaign has been fueled by special interests from outside the State of Indiana -- and this poll is just another example," responded Lugar campaign manager Emily Krueger. "Our internal polling shows Dick Lugar is, was and will remain in the lead. Our polling also shows Richard Mourdock's unfavorable ratings growing rapidly."
The primary is May 8.
The Wenzel Strategies survey of 601 likely Indiana Republican primary voters was conducted April 24-25 and carries a margin of error of +/- 4 percentage points.